Modern Plywood Bench From One Sheet of Scrap!

I spotted this beautiful scrap of plywood in a jumble of junk from a house renovation near me. I reckon it was used as part of a countertop, but I took it home not quite knowing what to do with it!

We've just moved into a new place, and there's a lovely big window facing south in our bedroom. "A bench would be perfect here," we thought.

After looking for some inspiration on Instructables and elsewhere, I came across this project from Remodelaholic with design from Curtis Frank Design (@curtisfrankdesign on Instagram). I loved the lines of this design, and the simple construction...

...but...

1. There's no workshop, table saw or pocket-hole jig in our one-bedroom flat.
2. I also thought the design missed a trick or two that would make it much stronger.
3. And I wanted to set myself the challenge of building this project with no fastenings of any kind.

I had a great time making this bench, and I learned a lot about woodworking - making something I really cared about from materials that I'd got for free was the perfect environment for learning. I made mistakes - which I'll highlight so you can avoid them - but I'm pleased with the result.

It's been a long time since my last Instructable, so here we go...

Materials you will need:

• A large sheet (or sheets) of 18mm (3/4 inch) plywood. Mine was approximately 1100mm x 800mm after trimming down the rotten bits. (This design would probably still work with hardwood, but I'm not a materials expert so I'm not sure on the strength. Plywood has good strength in all directions so is ideal for this. Equally if you're feeling adventurous, I'm sure this could be made from metal!)
• Wood glue (optional - mine has no glue, just held together by resistance in the material, but glue might be good if your joinery is a bit looser).

Essential tools:

• Pencil
• Ruler (steel rule is best)
• Tape measure
• Saw (I used a tenon saw for the whole project - I can't recommend this as it is VERY tedious when ripping lengths, but it can be done!)
• Chisels and hammer.
• Plane (perhaps not essential if you have a table saw or band saw, but my hand cuts are less than perfect...)

Optional tools:

• Square (If you don't have one, chances are there's a square on your saw handle.)
• Marking knife or craft knife (useful for marking cuts to minimise chipping, but not essential.)
• Protractor (otherwise you can construct the 15 degree angles using a pair of compasses and a ruler.
• Electric drill.
• Spirit level.

If you've just picked up a bit of scrap, the first thing you'll want to do is assess it. What we're looking for here is to work out the dimensions of the usable material, and any work we'll have to do to it.

In my case, there were some sections around the edge that were rotten, a big ol' hole in one corner, and some glue and screws in various places.

There was also a fair amount of discoloration due to water marks, and some scratches. I didn't care about this, all I wanted was to remove any structurally unsound material! You can always paint over discoloration later.

After scraping off the glue, removing screws and nails, I performed some emergency surgery but trimming off around 50mm from the right and bottom edges (as shown in the picture). I inspected the wood after this trim, and there was no rot, so I felt confident to continue.

As mentioned, the lines for this design came from this project from Remodelaholic with design from Curtis Frank Design.

My challenge was to create a design that was stronger, used no mechanical fastenings, and fit the material I had available.

I decided to create overlapping grooves in the two legs and a vertical support piece, as shown in the design. This would provide strength in all lateral directions.

To resist torsional forces, and provide stability for the bench top, I decided that an angled mortise and tenon joint would be ideal. If I could pull it off, it would also look good as well.

Overall the bench is made of four pieces:

1. The bench top - rectangular - in my case this was 240mm wide by approximately 1140mm long
2. The vertical support piece - a trapezoid with angled cuts at 15 degrees to accommodate legs - here was 170mm tall and approximately 1000mm long
3. Leg 1 - rectangular with straight cuts to slot into vertical support piece, two tenons at the top to slot into bench top - approximately 240mm wide (same as bench top) and 450mm long
4. Leg 2 - identical to Leg 1.

Your dimensions may vary depending on what size wood you have. I also chose a 15 degree angle because I thought it looked good whilst retaining strength, but you could go for a shallower angle or even no angle at all, I'm fairly confident the design would work well. I'd recommend you make your own sketch, and a scale diagram to get confidence in the design you've chosen.

Once you've got the dimensions how you like it, mark up your board! And remember...

...measure twice, cut once!

Once you've marked up the board, checked your measurements, go ahead and cut. Be safe, make sure you keep your hands well away from any powered machinery if you're using any.

If you're cutting by hand, I'd recommend checking out this really helpful video by Matt Estlea on How to Saw Correctly.

Once you're done, you should have four pieces that match your sketch.

This step has two main aims.

1. Get the legs as identical as possible.
2. Cut the angles on the end to ensure the bench sits flat on the floor.

For step 1, its a case of lining them up against each other (helpful at this point to mark a 'top' and a 'bottom' with your trusty pencil) and then using a plane or sander to remove material where needed to get them identical.

Tip: when planing or sanding down material, it helps to mark the line with a pencil to ensure you don't go too far (see picture 2).

For step 2, you need to get a 15 degree angle and mark it across the end (imagine the leg standing up on the ground, you will need to take some material off each end). To do this you can use a protractor, print out a 15 degree angle if you trust your printer, or if you're feeling like you want high precision and love some geometry, you can construct one using a straight edge and compass like I did! (Handy tutorial link.)

If you have a table saw, I'm told this step will be very easy, if not then just take your time to mark and start the cut, and let the saw do the work. You can always straighten out the cut later.

Revisit step 1 to double check they're still identical!

There's only really one crucial part here, and that's to make sure the top of the support (where it meets the bench top) is as straight as an arrow. So get your planer or sander, and a straight edge (see tip below) and get working!

Tip: you can check for straight edges against a glass table or mirror, as glass is usually machined to a high precision and is very resistant to warping and bending.

Not much to do here, other than to check for warping in the board, and to straighten up the edges. My plywood was slightly convex, I've tried to show it in picture 2. To correct this, I followed a really handy guide at ThePlywood.com which worked a treat.

This is the part that requires most concentration, but if you keep referring to the reference drawing you made in step 3, you should be golden. The key here is to remember that you need the grooves to be as wide as your board is thick (in my case 18mm). It's best to cut slightly under this, and widen out with a chisel - if the grooves are too wide, the bench may wobble and it won't be as strong.

I started with the vertical support piece, using my previously drawn 15 degree angle as a guide, and marked the grooves about 90mm in from either end - this is a balance between having them too close to the end you risk cracking the support piece, and too close in that the legs are too narrow and the bench is unstable. I probably could have cut them a bit closer to the edge.

The grooves should extend to halfway up the board. Again when cutting, remember to take your time. I made two cuts on either side of the groove and removed the material using a chisel at the end.

For the legs, the grooves should be cut exactly in the middle of the board. Here though, they are slightly longer, as they need to accommodate the remainder of the vertical support piece, and extend up through the bench top.

To help mark this out, the easiest way is to lie the vertical support piece flat and place the legs on top in the same orientation as they would be in final assembly. use a scrap piece of plywood above the vertical support piece to gauge the extra length you need for the thickness of the bench top. (I've attached a diagram above). You'll then have to mark the middle of the board using your ruler.

Once you've cut the grooves, clean them up with the chisel until you can slot them into place, and check for level. You may need to expand the grooves on one side to make level.

This step requires patience, but is not too tricky if you take your time.

The twist with these mortise and tenon joints is they're angled. This means we have to cut an angled section of material away from the interior the bench top. Well, four to be precise.

You could do all sorts of complicated measurements with a ruler to get this, but I have a handy trick.

First assemble the legs and the vertical support slat until the grooves are fully overlapping. Place the bench top top side up and put the legs and support assembly upside down on top of this. The logic here is that the position the legs are in now is exactly where they need to "come up through" the bench top. Hopefully the attached image makes this process clear.

Ensure the legs and support assembly is evenly spaced from either end, and square to the edge of the board. Then make 8 marks on the bench top with your pencil for the edges of the mortises, and corresponding marks on the legs for the tenons. I set mine at 40mm, which is plenty wide enough. Keep the legs in exactly the same place throughout this process.

Remove the legs, and complete the rectangles, marking out the material to be removed.

Flip the bench top over (now the underside will be showing) and slide the legs out until they are flush with the top of the support piece. This is now the "entry point" for the tenons.

Follow the same marking process as the other side.

Great job! Take a breather, that's the tricky bit done!

For the tenons (on the legs) refer back to the diagram in step 3 to remind yourself of which material you're cutting away! Other than that it should be easy straight cuts on the legs to remove the material.

For the mortices, I used an electric drill, angled at 15 degrees to remove most of the material, then cleaned up the edges with a chisel. You can use a scrap piece of plywood to check whether they are wide enough.

Finally there, the tricky bits are all done, now time for it to come together.

Slot the legs back into the grooves, and push them up until they're flush with the top of the vertical support. Line the tenons and mortises up and push them in.

This may take a bit of effort! If you've cut your mortises and tenons right, they should just fit. I had to put all my weight on the legs to get them in, but it did work!

Take a well earned rest on your assembled bench.

I will leave the finishing up to you, I have currently left mine lightly sanded, although we may end up painting it later on.

Let me know what you think! And thanks for reading!